Recently, communication systems performing communication via communication networks such as the Internet have become widespread along with requests for reductions in business trip expenses and business trip times. Such a communication system establishes a session for transmitting and receiving content data such as image data and voice data between communication terminals, thereby achieving communication between the communication terminals.
It is known that IP phone communication systems perform, when establishing a session between communication terminals, control in accordance with the state of a communication terminal in order to appropriately performing connection between the communication terminals. For example, communication terminals perform processing that causes a caller communication terminal to output a sound indicating being busy when an opposite communication terminal is busy and causes the caller communication terminal to output a dial tone when the opposite communication terminal is in a standby state.
In teleconference communication systems, it is known that a teleconference management system controls a session between communication terminals (refer to Patent Literature 1). In this case, a plurality of teleconference terminals are connected to one teleconference management system, and based on a request from each of the teleconference terminals, the teleconference management system controls the session. Owing to this, when the number of the teleconference terminals connected to the teleconference management system increases, a large load related to the control is imposed on the teleconference management system.
As a method for distributing a load imposed on a server, a method is disclosed that selects a server that performs processing out of a plurality of servers (refer to Patent Literature 2). According to this disclosure, each of the servers determines which of the server and another server is to perform processing in response to a processing request from a client, based on the load of the server and the load of the other server.
However, a load imposed on a controller that controls a session between communication terminals changes in accordance with situations, and a problem arises in that, when a controller to be connected to a communication terminal is selected out of a plurality of controllers, an attempt to distribute the load by selecting a controller with a smaller load requires complicated processing such as measuring the load of each of the controllers for each selection.